scholarly journals Inhibition of DNA synthesis in SV3T3 cultures by isolated 3T3 plasma membranes.

1983 ◽  
Vol 97 (1) ◽  
pp. 276-279 ◽  
Author(s):  
S W Peterson ◽  
V Lerch
Keyword(s):  
Plasma Membrane ◽  
Dna Synthesis ◽  
Cell Cultures ◽  
Plasma Membranes ◽  
Inhibitory Effect ◽  
Density Dependent ◽  
Inhibition Of Growth ◽  
Dependent Inhibition ◽  
Membrane Components ◽  
Inhibition Of Dna Synthesis

3T3 plasma membranes were added to subconfluent cultures of SV3T3 cells in the presence of fusogens. If this protocol results in the introduction into the SV3T3 cell membrane of 3T3 plasma membrane components responsible for density-dependent inhibition of growth, then the SV3T3 cell cultures would be expected to show decreased rates of DNA synthesis as they approach confluence. Results of these experiments indicate that rates of DNA synthesis in SV3T3 cultures so treated were as much as 63% less than in untreated controls. This effect could not be attributed to the fusogens or to the 3T3 plasma membranes alone. This growth-inhibitory effect is specific for 3T3 membranes and is not observed when SV3T3 plasma membranes are fused with SV3T3 cell cultures. These data support the hypothesis that one aspect of the loss of density-dependent inhibition of growth in SV3T3 cells is a deletion or alteration in plasma membrane components and, further, that density-dependent inhibition of growth can be in part restored to SV3T3 cell cultures by fusing the cells with 3T3 plasma membranes.

scholarly journals Pseudotypes of Vesicular Stomatitis Virus with CD4 Formed by Clustering of Membrane Microdomains during Budding

2005 ◽  
Vol 79 (11) ◽  
pp. 7077-7086 ◽  
Author(s):  
Erica L. Brown ◽  
Douglas S. Lyles
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Lipid Rafts ◽  
Immunoelectron Microscopy ◽  
Vesicular Stomatitis Virus ◽  
Plasma Membranes ◽  
Membrane Microdomains ◽  
Virus Budding ◽  
Vesicular Stomatitis ◽  
Membrane Components

ABSTRACT Many plasma membrane components are organized into detergent-resistant membrane microdomains referred to as lipid rafts. However, there is much less information about the organization of membrane components into microdomains outside of lipid rafts. Furthermore, there are few approaches to determine whether different membrane components are colocalized in microdomains as small as lipid rafts. We have previously described a new method of determining the extent of organization of proteins into membrane microdomains by analyzing the distribution of pairwise distances between immunogold particles in immunoelectron micrographs. We used this method to analyze the microdomains involved in the incorporation of the T-cell antigen CD4 into the envelope of vesicular stomatitis virus (VSV). In cells infected with a recombinant virus that expresses CD4 from the viral genome, both CD4 and the VSV envelope glycoprotein (G protein) were found in detergent-soluble (nonraft) membrane fractions. However, analysis of the distribution of CD4 and G protein in plasma membranes by immunoelectron microscopy showed that both were organized into membrane microdomains of similar sizes, approximately 100 to 150 nm. In regions of plasma membrane outside of virus budding sites, CD4 and G protein were present in separate membrane microdomains, as shown by double-label immunoelectron microscopy data. However, virus budding occurred from membrane microdomains that contained both G protein and CD4, and extended to approximately 300 nm, indicating that VSV pseudotype formation with CD4 occurs by clustering of G protein- and CD4-containing microdomains.

scholarly journals DNA synthesis by ovine mammary alveolar epithelial cells: effects of heparin, epidermal growth factor-related peptides and interaction with stage of pregnancy

1998 ◽  
Vol 156 (2) ◽  
pp. 283-290 ◽  
Author(s):  
IA Forsyth ◽  
JA Taylor ◽  
CD Moorby
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Epithelial Cells ◽  
Dna Synthesis ◽  
Cell Cultures ◽  
Inhibitory Effect ◽  
Alveolar Epithelial Cells ◽  
Alveolar Epithelial ◽  
Pregnant Sheep ◽  
Epidermal Growth

Amphiregulin is a heparin-binding member of the epidermal growth factor (EGF) family, which we have recently shown to be expressed in sheep mammary gland. Uniquely among known EGF-like growth factors, its mitogenic activity is inhibited by soluble heparin, but heparin-like molecules on the cell surface and/or in extracellular matrix appear to be necessary for amphiregulin to exert its biological effect. In primary cultures of sheep mammary alveolar epithelial cells, heparin (1-20 mg/l) inhibited DNA synthesis in a dose-dependent manner. The extent of the inhibition was influenced by physiological state, being greater (P < 0.05) in mammary cell cultures derived from 5- to 10-week pregnant sheep (63.1 +/- 8.2%, mean +/- S.E.M., n = 8) than in cultures derived from sheep which were non-pregnant (35.8 +/- 8.3% inhibition, n = 6) or late, 20-week, pregnant (39.8 +/- 5.6%, n = 6). Both EGF and transforming growth factor-alpha (TGF-alpha) significantly (P < 0.001) increased DNA synthesis in the presence of heparin. The effect of TGF-alpha was dose-related, wholly reversing the inhibitory effect of heparin in cell cultures from non-pregnant and 20-week pregnant sheep. DNA synthesis was stimulated by amphiregulin and TGF-alpha increased the maximum response. The heparin antagonist, hexadimethrine, inhibited DNA synthesis, but, in the presence of amphiregulin, approximately equivalent concentrations of heparin overcame this inhibitory effect. In the presence of heparin, TGF-alpha showed synergistic interactions with insulin or IGF-I. The results indicate interactive effects of EGF and IGF growth factor families in sheep mammary growth.

scholarly journals Modulation of 5′-nucleotidase activity in plasma membranes and intact cells by the extracellular matrix proteins laminin and fibronectin

1992 ◽  
Vol 282 (1) ◽  
pp. 181-188 ◽  
Author(s):  
N Olmo ◽  
J Turnay ◽  
G Risse ◽  
R Deutzmann ◽  
K von der Mark ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Plasma Membrane ◽  
Inhibitory Activity ◽  
Plasma Membranes ◽  
Extracellular Matrix Proteins ◽  
Cell Receptor ◽  
Inhibitory Effect ◽  
Matrix Proteins ◽  
Nucleotidase Activity ◽  
Intact Cells

Modulation of 5′-nucleotidase activity by the extracellular matrix proteins fibronectin, laminin and their fragments has been studied in plasma membrane preparations as well as in intact BCS-TC2 and Rugli cells. The ectoenzyme on plasma membranes is activated by laminin; fibronectin inhibits the AMPase activity on BCS-TC2 plasma membranes but no inhibitory effect is found in plasma membrane preparations from Rugli cells. These effects are dependent on the preincubation time and protein concentration. When the effect of the extracellular matrix proteins is studied on intact cells, both BCS-TC2 and Rugli cells show similar behaviour. A decrease in the enzyme activity is observed in the presence of fibronectin. The AMPase inhibitory activity is located on its 40 kDa fragment. No inhibitory activity is found in other fibronectin fragments, including the 140 kDa fragment which contains the RGDS cell-adhesion sequence. Laminin and its E1-4 and E8 fragments are able to activate the ecto-5′-nucleotidase activity of both BCS-TC2 and Rugli cells. The effect of the E1-4 fragment on intact cells is greater than that observed for the E8 fragment and uncleaved laminin. Our results suggest a bifunctional role for 5′-nucleotidase as ectoenzyme and cell receptor for extracellular matrix proteins.

Inhibition of Growth and DNA Synthesis in Cell Cultures by Cyclic Amp

1974 ◽  
Vol 16 (2) ◽  
pp. 301-307
Author(s):  
P. EKER
Keyword(s):  
Cyclic Amp ◽  
Dna Synthesis ◽  
Cell Cultures ◽  
Degradation Products ◽  
Liver Cells ◽  
Soluble Cell ◽  
Inhibition Of Growth ◽  
Insoluble Material ◽  
Rna And Protein Synthesis ◽  
Soluble Cell Fraction

Cyclic AMP (0.1 to 1 mM) was found to inhibit the growth of human liver cells in monolayer cultures. Significant amounts of degradation products were not detected in the medium indicating that the growth-inhibiting effect was associated with the intact cyclic nucleotide. DNA synthesis in the liver cell cultures, as measured by thymidine incorporation into acid-insoluble material, was markedly inhibited by cyclic AMP. RNA and protein synthesis were not significantly affected. Cyclic AMP induced a considerable increase in the cellular uptake of thymidine and uridine from the medium. When the liver cells were incubated in medium containing radioactive cyclic AMP, no labelled cyclic AMP could be detected in the acid-soluble cell fraction by chromatographic analysis. It is suggested that cyclic AMP does not enter the liver cells, but that its action on growth and DNA synthesis is somehow mediated through an interaction with the cell surface.

Release from Density-Dependent Inhibition of Growth in the Absence of Cell Locomotion

1974 ◽  
Vol 16 (1) ◽  
pp. 181-188
Author(s):  
MARGARET M. YARNELL ◽  
H. P. SCHNEBLI
Keyword(s):  
Insulin Treatment ◽  
Density Dependent ◽  
Mouse Fibroblasts ◽  
Cell Locomotion ◽  
Inhibition Of Growth ◽  
Dependent Inhibition ◽  
Cellular Locomotion

3T3 mouse fibroblasts are released from density-dependent inhibition of growth by treatment with insulin. The same insulin treatment stimulates cell locomotion several hours before any new mitoses become visible. Inhibition of cell locomotion by colcemid does not affect the overgrowth stimulation due to insulin. From this it is concluded that cellular locomotion is not a prerequisite for the release from density-dependent inhibition of growth.

Growth in vitro of tumour cell × fibroblast hybrids in which malignancy is suppressed

1977 ◽  
Vol 25 (1) ◽  
pp. 73-86
Author(s):  
D.S. Straus ◽  
J. Jonasson ◽  
H. Harris
Keyword(s):  
Tumour Cell ◽  
Cloning Efficiency ◽  
Density Dependent ◽  
Inhibition Of Growth ◽  
Dependent Inhibition ◽  
Soft Agarose

We have studied the growth in vitro of a lymphoma × fibroblast hybrid and several melanoma × fibroblast hybrids in which malignancy is suppressed. The parental cells, the hybrids, and malignant segregants derived from the hybrids were analysed for serum requirement, cloning efficiency in soft agarose, density-dependent inhibition of growth, and secretion of plasminogen-activating enzyme. One malignant segregant from the lymphoma × fibroblast cross was found by a number of criteria to have a more highly ‘transformed’ phenotype than the hybrid from which it was derived. However, in the case of the melanoma × fibroblast crosses, none of the parameters examined could be correlated in a direct way with malignancy.

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